Perfluoroether sealant compositions

ABSTRACT

Disclosed are perfluoroethers and perfluoroether compositions useful in high temperature aerospace applications. The perfluoroethers can be adapted for use with various curing chemistries.

FIELD

This disclosure relates to perfluoroethers and perfluoroethercompositions useful in high temperature aerospace sealant applications.

BACKGROUND

Electrically conductive sealants are widely used in the aerospaceindustry to seal gaps between two panels where electrical conductivityis required. However, maintaining electrical conductivity after exposureto high temperature, such as 500° F. for 24 hours, remains an unmetneed. Fluoropolymers, such as perfluoroethers, have been developed thatexhibit high temperature stability. Perfluoroethers are useful for hightemperature applications and the terminal groups may be adapted forvarious curing chemistries. However, to meet the demanding performancerequirements of the aerospace industry, especially in applications inwhich high electrical conductivity is required, perfluoroethercompositions must be carefully tailored.

SUMMARY

To provide sealants meeting the demanding environmental, thermal,chemical, and electrical requirements of aerospace applications,addition- and moisture-curable sealant compositions containing modifiedpolymeric perfluoroethers are disclosed. Perfluoroethers provided by thepresent disclosure have been extended using siloxanes to increase themolecular weight of the perfluoroethers. The terminal groups have alsobeen modified to include hydrosilane groups appropriate for use withaddition curing, or with alkoxysilane groups useful for moisture curing.Addition-curable and moisture-curable compositions are provided having acombination of perfluoroethers including extended perfluoroethers. Suchcompositions are particularly useful in electrically conductivesealants.

In a first aspect, moisture-curable compositions comprising analkoxysilane-terminated extended perfluoroether are disclosed.

In a second aspect, moisture-curable compositions are disclosedcomprising the reaction products of reactants comprising: (a) anunextended alkenyl-terminated perfluoroether; (b) ahydrosilane-terminated siloxane; and (c) an alkoxysilane.

In a third aspect, moisture-curable compositions are disclosed preparedby steps comprising: (a) reacting an unextended alkenyl-terminatedperfluoroether and a hydrosilane-terminated siloxane to provide amixture of alkenyl-terminated extended perfluoroethers and unextendedalkenyl-terminated perfluoroethers; and (b) reacting the mixture with analkoxysilane to provide a mixture of alkoxysilane-terminated extendedperfluoroethers and unextended alkoxysilane-terminated perfluoroethers.

In a fourth aspect, addition-curable compositions comprising (a) analkenyl-terminated perfluoroether; and (b) a hydrosilane-terminatedextended perfluoroether are disclosed.

In a fifth aspect, addition-curable compositions are disclosedcomprising the reaction products of reactants comprising: (a) analkenyl-terminated perfluoroether; (b) a first hydrosilane-terminatedsiloxane; and (c) a second hydrosilane-terminated siloxane.

In a sixth aspect, addition-curable compositions are disclosed preparedby steps comprising: (a) reacting an unextended alkenyl-terminatedperfluoroether and a first hydrosilane-terminated siloxane to provide amixture of alkenyl-terminated extended perfluoroethers and unextendedalkenyl-terminated perfluoroethers; and (b) reacting the mixture with asecond hydrosilane-terminated siloxane to provide a mixture ofhydrosilane-terminated extended perfluoroethers and unextendedhydrosilane-terminated perfluoroethers.

In a seventh aspect, cured sealants comprising a composition provided bythe present disclosure are disclosed.

In an eighth aspect, apertures sealed with a composition provided by thepresent disclosure are disclosed.

In a ninth aspect, methods of sealing an aperture are disclosed,comprising (a) applying a composition provided by the present disclosureto one or more surfaces defining an aperture; (b) assembling thesurfaces defining the aperture; and (c) curing the composition to sealthe aperture.

DETAILED DESCRIPTION DEFINITIONS

For purposes of the following description, it is to be understood thatembodiments provided by the present disclosure may assume variousalternative variations and step sequences, except where expresslyspecified to the contrary. Moreover, other than in the examples, orwhere otherwise indicated, all numbers expressing, for example,quantities of ingredients used in the specification and claims are to beunderstood as being modified in all instances by the term “about.”Accordingly, unless indicated to the contrary, the numerical parametersset forth in the following specification and attached claims areapproximations that may vary depending upon the desired properties to beobtained. At the very least, and not as an attempt to limit theapplication of the doctrine of equivalents to the scope of the claims,each numerical parameter should at least be construed in light of thenumber of reported significant digits and by applying ordinary roundingtechniques.

Notwithstanding that the numerical ranges and parameters setting forththe broad scope of the invention are approximations, the numericalvalues set forth in the specific examples are reported as precisely aspossible. Any numerical value, however, inherently contains certainerrors necessarily resulting from the standard variation found in theirrespective testing measurements.

Also, it should be understood that any numerical range recited herein isintended to include all sub-ranges encompassed therein. For example, arange of “1 to 10” is intended to include all sub-ranges between (andincluding) the recited minimum value of about 1 and the recited maximumvalue of about 10, that is, having a minimum value equal to or greaterthan about 1 and a maximum value of equal to or less than about 10.Also, in this application, the use of “or” means “and/or” unlessspecifically stated otherwise, even though “and/or” may be explicitlyused in certain instances.

A dash (“-”) that is not between two letters or symbols is used toindicate a point of bonding for a substituent or between two atoms. Forexample, —CONH₂ is bonded to another chemical moiety through the carbonatom.

“Alkenyl” refers to a group —CH═CH₂.

“Alkoxysilane” refers to a compound of Formula (4) or a group of Formula(4a):H—Si(—R³)_(p)(—OR³)_(3-p)  (4)—Si(—R³)_(p)(—OR³)_(3-p)  (4a)where p is selected from 0, 1, and 2; and each R³ is independentlyselected from C₁₋₄ alkyl. In certain embodiments of a compound ofFormula (4) and a group of Formula (4a), p is 0, p is 1, and in certainembodiments, p is 2. In certain embodiments of a compound of Formula (4)and a group of Formula (4a), each R³ is independently selected fromethyl and methyl. In certain embodiments of a compound of Formula (4)and a group of Formula (4a), each R³ is ethyl, and in certainembodiments, each R³ is methyl.

“Alkyl” refers to a monoradical of a saturated, branched orstraight-chain, acyclic hydrocarbon group having, for example, from 1 to20 carbon atoms, from 1 to 10 carbon atoms, from 1 to 6 carbon atoms,from 1 to 4 carbon atoms, or from 1 to 3 carbon atoms. In certainembodiments, the alkyl group is C₂₋₆ alkyl, C₂₋₄ alkyl, and in certainembodiments, C₁₋₃ alkyl. Examples of alkyl groups include methyl, ethyl,n-propyl, iso-propyl, n-butyl, iso-butyl, tert-butyl, n-hexyl, n-decyl,tetradecyl, and the like. In certain embodiments, the alkyl group isC₁₋₆ alkyl, C₁₋₄ alkyl, C₁₋₃ alkyl, and in certain embodiments, C₁₋₂alkyl.

“Siloxane” refers to compounds or moieties having alternating siliconand oxygen atoms such as —Si(R)₂—O—Si(R)₂— where each R can be, forexample, alkyl, cycloalkyl, alkoxysilane, aryl, and others. In certainembodiments, a siloxane comprises the structure of Formula (2a), Formula(2b), or Formula (2c):

where each R¹ is independently selected from C₁₋₄ alkyl, C₅₋₆cycloalkyl, phenyl, and —O—Si(R²)_(3-m) (H)_(m) or —O—Si(R²)³, whereeach R² is independently C₁₋₄ alkyl, m is selected from 0, 1, and 2; andn is an integer from 1 to 6. Siloxanes of Formula (2a) and Formula (2c),and siloxanes of Formula (2b) in which at least one R² is—O—Si(R²)_(3-m)(H)_(m) and m is 1 or 2 are referred tohydrosilane-terminated siloxanes. In certain embodiments of siloxanes ofFormula (2a) and Formula (2b), each R¹ is independently selected fromC₁₋₄ alkyl, C₅₋₆ cycloalkyl, phenyl, and —O—Si(R²)₃, wherein each R² isindependently C₁₋₄ alkyl; and n is an integer from 1 to 6.

A siloxane may also be cyclic and, for example, and may have thestructure,

where each R¹ can be, for example, hydrogen, alkyl, cycloalkyl,—O—Si(R²)_(3-m)(H)_(m) aryl, and others, and n can be 1, 2, 3, 4, or aninteger greater than 4. An example of a cyclic siloxane istetramethylcyclotetrasiloxane (TMCTS). Cyclic siloxanes having at leastone hydrosilane group are referred to as hydrosilane-terminatedsiloxanes.

As can be appreciated, siloxanes also include alicyclic siloxanes havingboth linear and cyclic siloxane structures.

Siloxanes also include aliphatic siloxanes, e.g., siloxanes of Formula(2a), Formula (2b), and Formula (2c) in which each R¹ is selected fromhydrogen and C₁₋₄ alkyl. In certain embodiments of an aliphaticsiloxane, each R¹ is selected from hydrogen, C₁₋₄ alkyl, C₃₋₆cycloalkyl, and phenyl.

“Hydrosilane” refers to a group having at least one hydrogen bonded to asilicon atom such as, for example, —SiH₃, —Si(—R)H₂, and —Si(—R)₂H,where each R is a group other than hydrogen such as, for example, a C₁₋₄alkyl, C₅₋₆ cycloalkyl, phenyl, or —O—Si(R²)_(3-m)(H)_(m), where each R²is independently C₁₋₄ alkyl; and m is selected from 0, 1, and 2. Incertain embodiments, a hydrosilane group refers to a —Si(R)₂H group. Incertain embodiments, a hydrosilane group is a —Si(R)₂H group whereineach R is independently selected from C₁₋₄ alkyl, C₅₋₆ cycloalkyl,phenyl, and a —O—Si(R²)_(3-m)(H)_(m), where each R² is independentlyC₁₋₄ alkyl; and m is selected from 0, 1, and 2. A hydrosilane-terminatedcompound, moiety, or group, refers to a compound, moiety, or grouphaving a hydrosilane group. A hydrosilane-terminated siloxane refers toa siloxane having one or more hydrosilane groups such as, for example,siloxanes of Formula (2a), and Formula (2c), and compounds of Formula(2b) where at least one R¹ is —O—Si(R²)_(3-m)(H)_(m) and m is 1 or 2.

Reference is now made to certain embodiments of compounds, polymers,compositions, and methods. The disclosed embodiments are not intended tobe limiting of the claims. To the contrary, the claims are intended tocover all alternatives, modifications, and equivalents.

Perfluoroethers

Perfluoroethers are known to be useful in applications requiring hightemperature stability. Perfluoroether polymers are available, forexample, from suppliers such as Daikin (Demnum®), Solvay (Fomblin®), andShin-Etsu (Sifel®). In general, certain perfluoroether polymers arecharacterized by a backbone containing multiple perfluoroether —CF₂—O—units, such as, for example, —(CF₂—CF₂—CF₂—O)_(k)— (Demnum®),—(CF₂—CF₂—O)_(k)—(CF₂—O)_(m)— (Fomblin®), and —(CF(CF₃)—CF₂—O)_(k)— or—CF₂—CF₂(CF₃)—O)_(k)— (Sifel®) perfluoroether groups. In certainembodiments, a perfluoroether comprises a perfluoroether group selectedfrom —[—CF₂—O—]_(k)—; —[—CF(CF₃)—O—]_(k)—; —[—CF₂—CF₂—O—]_(k)—;—[—CF(CF₃)—CF₂—O—]_(k)—; —[—CF₂—CF(CF₃)—O—]_(k)—;—[—CF₂—CF₂—CF₂—O—]_(k)—; —[—CF(CF₃)—CF₂—CF₂—O—]_(k)—;—[—CF₂—CF(CF₃)—CF₂—O—]_(k)—; —[—CF₂—CF₂—CF(CF₃)—O—]_(k)—;—CF₂—O—[—CF₂—CF₂—O—]_(k)—[—CF₂—O—]_(k)—CF₂—;—CF₂—O—[—CF(CF₃)—CF₂—O—]_(k)—[—CF₂—O—]_(k)—CF₂—;—CF₂—O—[—CF₂—CF(CF₃)—O—]_(k)—[—CF₂—O—]_(k)—CF₂—; and a combination ofany of the foregoing. In certain embodiments, k is an integer from 2 to100, from 5 to 80, from 10 to 60, and in certain embodiments, from 15 to60. In certain embodiments, the total number of perfluoroether groupsincluding any of those described herein, either individually or incombination, may be from 2 to 100, from 5 to 80, from 10 to 60, and incertain embodiments, from 15 to 60. In certain embodiments, aperfluoroether has a number average molecular weight from 500 Daltons to15,000 Daltons, from 1,000 Daltons to 12,000 Daltons, from 1,500 Daltonsto 10,000 Daltons, and in certain embodiments, from 2,000 Daltons to8,000 Daltons.

Extended perfluoroethers provided by the present disclosure compriseabout twice the number perfluoroether groups as the correspondingunextended perfluoroether, such as, for example, from 2 to 300, from 10to 250, from 30 to 200, from 50 to 150, and in certain embodiments, from100 to 150. In certain embodiments, a extended perfluoroethers have anumber average molecular weight from 1,000 Daltons to 40,000 Daltons,from 2,000 Daltons to 30,000 Daltons, from 5,000 Daltons to 25,000Daltons, and in certain embodiments, from 10,000 Daltons to 25,000Daltons.

In certain embodiments, an alkenyl-terminated perfluoroether comprisesperfluoroether groups selected from —[—CF₂—CF₂—CF₂—O—]_(k)—,—CF₂—O—[—CF₂—CF₂—O—]_(k)—[—CF₂—O—]_(k)—CF₂—, —[—CF(CF₃)—CF₂—O—]_(k)—,—[—CF₂—CF(CF₃)—O—]_(k)—, and a combination of any of the foregoing, andin certain embodiments, each k is independently an integer from 2 to100.

In certain embodiments, a perfluoroether comprises perfluoroether groupshaving the structure —[—CF(CF₃)CF₂—O—]_(k)— where k is an integer from 2to 200, from 10 to 180, from 20, to 160, from 50 to 150, and in certainembodiments, from 100 to 150.

In certain embodiments, a perfluoroether comprises perfluoroether groupshaving the structure —[—CF₂CF(CF₃)—O—]_(k)— where k is an integer from 2to 200, from 10 to 180, from 20, to 160, from 50 to 150, and in certainembodiments, from 100 to 150.

In certain embodiments, a perfluoroether comprises an alkenyl-terminatedperfluoroether. In certain embodiments an alkenyl-terminatedperfluoroether has an average alkenyl functionality from 2 to 6, and incertain embodiments, from 2 to 3. In certain embodiments, analkenyl-terminated perfluoroether is difunctional. In certainembodiments, polyfunctional alkenyl-terminated perfluoroethers may beprepared by reacting a difunctional alkenyl-terminated perfluoroetherwith a polyfunctional hydrosilane. Examples of polyfunctionalhydrosilanes include alkylsilanes such as ethylsilane and others such asphenyltris(dimethylsilyl)silane. Reacting, for example, a difunctionalalkenyl-terminated perfluoroether and a polyfunctional alkylsilaneR—SiH₃ where R is alkyl, in a 3:1 equivalent ratio can provide atrifunctional alkyl-terminated perfluoroether. It can be appreciatedthat alkenyl-terminated perfluoroethers having various alkenylfunctionality, ranges of functionality, and/or average alkenylfunctionality may be prepared.

In certain embodiments, a perfluoroether includes segments in additionto perfluoroether —CF₂—O— units, including any of the perfluoroethergroups disclosed herein. The additional segments may be situated at anylocation within the backbone structure such as, for example, separatingsegments containing multiple perfluoroether groups or between theperfluoroether backbone and an end group or terminal group. Using one ofthe perfluoroether segments as an example, a perfluoroether having oneor more additional segments may include backbone regions having thestructure -L-[—CF₂—O—]_(k)—, -L-[—CF₂—O—]_(k)-L-,-L-[—CF₂—O—]_(k)-L-[—CF₂—O—]_(k)—, and/or others, where -L- representsthe additional segment. The one or more additional segment may include,for example, alkanediyl groups, cycloalkanediyl groups, arene-diylgroups, amine-diyl, silane-diyl, and combinations of any of theforegoing, which may be unsubstituted or substituted where thesubstituents may be, for example, alkyl, amine, hydroxy, ═O, or alkoxy.

Thus, as used herein, -PFE- refers to the core of the perfluoroether andcomprises at least one perfluoroether segment or segments, -PFE_(s)-,where each perfluoroether segment comprises perfluoroether groups, andany additional non-perfluoroether segments -L- such as, for example,-L-PFE_(s)-L-. The perfluoroether core -PFE- may be terminated with afunctional group such as an alkenyl group or other functional group.

In certain embodiments, a perfluoroether is a difunctionalperfluoroether. In certain embodiments, a difunctionalalkenyl-terminated perfluoroether has the structure CH₂═CH-PFE-CH═CH₂,wherein -PFE- comprises multiple perfluoroether groups and anynon-perfluoroether segments. In certain embodiments, a difunctionalalkenyl-terminated perfluoroether has the structureCH₂═CH-L-PFE_(s)-L-CH═CH₂, where L is defined herein.

Extended Perfluoroethers

In certain embodiments of compositions provided by the presentdisclosure, a composition comprises an extended perfluoroether.

An extended perfluoroether refers to a perfluoroether resulting from thereaction of a lower molecular weight perfluoroether with an extendinggroup. Extension of prepolymers to form higher molecular weight polymersis well-known and can be controlled at least in part by selection of theratio of functional groups of the reactants. In certain embodiments, anextended perfluoroether comprises two precursor perfluoroethers, threeprecursor perfluoroethers, four precursor perfluoroethers, and incertain embodiments, more than four precursor perfluoroethers. Incertain embodiments, an extending group is a siloxane. Use of certainsiloxanes as extending groups may also be useful to impart additionalhydrosilane functionality as useful for addition curing(hydrosilylation) reactions.

In certain embodiments, an extended perfluoroether comprises terminalgroups selected from alkenyl groups, hydrosilane groups,hydrosilane-terminated siloxane groups, and alkoxysilane groups. Incertain embodiments, an extended perfluoroether comprises terminalalkenyl groups, in certain embodiments, terminal siloxane groups,terminal hydrosilane-terminated siloxane groups, and in certainembodiments, terminal alkoxysilane groups.

In certain embodiments, an alkenyl-terminated extended perfluoroetherhas the structure of Formula (1):CH₂═CH-PFE-CH₂—CH₂-A′-CH₂—CH₂-PFE-CH═CH₂  (1)wherein -A′- has the structure:

where each R¹ is independently selected from C₁₋₄ alkyl, C₅₋₆cycloalkyl, phenyl, and —O—Si(R²)_(3-m)(H)_(m) or —O—Si(R²)₃, where eachR² is independently C₁₋₄ alkyl, m is selected from 0, 1, and 2; and n isan integer from 1 to 6; and each —CH₂—CH₂-PFE-CH₂—CH₂— is derived froman alkenyl-terminated perfluoroether, CH₂═CH-PFE-CH═CH₂, where -PFE-comprises perfluoroether groups.

In certain embodiments of Formula (2b), n is 1, n is 2, n is 3, n is 4,n is 5, and in certain embodiments, n is 6.

In certain embodiments of Formula (2b), each R¹ is independentlyselected from C₁₋₂ alkyl, phenyl, and —O—Si(R³)₃. In certain embodimentsof Formula (2b), each R¹ is independently selected from C₁₋₂ alkyl,phenyl, and —O—Si(R³)₃, where each R³ is independently selected fromC₁₋₂ alkyl. In certain embodiments of Formula (2b), each R¹ isindependently selected from C₁₋₂ alkyl, phenyl, and —O—Si(CH₃)₃. Incertain embodiments of Formula (2b), n is selected from 1 and 2; andeach R¹ is independently selected from C₁₋₂ alkyl, phenyl, and—O—Si(CH₃)₃.

In certain embodiments of Formula (2b), each R¹ is independentlyselected from C₁₋₂ alkyl, phenyl, —OSi(CH₃)₂H, and —OSi(CH₃)₃. Incertain embodiments of Formula (2b), n is selected from 1 and 2; andeach R¹ is independently selected from C₁₋₂ alkyl, phenyl, —OSi(CH₃)₂H,and —OSi(CH₃)₃. In certain embodiments, n is selected from 1 and 2; andeach R¹ is independently selected from —CH₃ and —OSi(CH₃)₂H.

In certain embodiments of Formula (2b), each R¹ is independentlyselected from C₁₋₄ alkyl, C₅₋₆ cycloalkyl, phenyl, and —O—Si(R²)₃,wherein each R² is independently C₁₋₄ alkyl; and n is an integer from 1to 6.

In certain embodiments of a hydrosilane-terminated siloxane of Formula(2b), each R¹ is the same and in certain embodiments, at least one R¹ isdifferent. In certain embodiments, each R¹ is selected from methyl,ethyl, n-propyl, isopropyl, n-butyl, iso-butyl, and tert-butyl. Incertain embodiments, each R¹ is selected from methyl and ethyl. Incertain embodiments, each R¹ is methyl.

Extended perfluoroethers suitable for moisture-curable compositions donot contain terminal hydrosilane groups, such that R¹ is —O—Si(R²)₃.

In certain embodiments, an alkenyl-terminated extended perfluoroethercomprises the reaction products of reactants comprising: (a) anunextended alkenyl-terminated perfluoroether; and (b) ahydrosilane-terminated siloxane.

An alkenyl-terminated perfluoroether may comprise any of theperfluoroether groups disclosed herein and in certain embodiments, anunextended alkenyl-terminated perfluoroether comprises perfluoroethergroups selected from —[—CF₂—CF₂—CF₂—O—]_(k)—,—CF₂—O—[—CF₂—CF₂—O—]_(k)—[—CF₂—O—]_(k)—CF₂—, —[—CF(CF₃)—CF₂—O—]_(k)—,—[—CF₂—CF(CF₃)—O—]_(k)— and a combination of any of the foregoing.

An unextended alkenyl-terminated perfluoroether such as an unextendedalkenyl-terminated perfluoroether of the formula CH₂═CH-PFE-CH═CH₂ maybe a commercially available perfluoroether such as a perfluoroetheravailable from Daikin, Solvay, Shin-Etsu, and others, or may be derivedfrom a commercially available perfluoroether that does not have terminalalkenyl groups.

In certain embodiments, an unextended alkenyl-terminated perfluoroetherhas a number-average molecular weight from 2,000 Daltons to 15,000Daltons, from 4,000 Daltons to 13,000 Daltons, from 5,000 Daltons to12,000 Daltons, from 6,000 Daltons to 11,000 Daltons, from 7,000 Daltonsto 10,000 Daltons, and in certain embodiments, from 8,000 Daltons to9,000 Daltons. In certain embodiments, an unextended alkenyl-terminatedperfluoroether is liquid at room temperature. In certain embodiments, anunextended alkenyl-terminated perfluoroether has a viscosity from 80poise to 400 poise, from 90 poise to 300 poise, from 100 poise to 200poise, and in certain embodiments, from 110 poise to 150 poise, at 25°C. In certain embodiments, an unextended alkenyl-terminatedperfluoroether has a viscosity from 0.2 poise to 400 poise, from 0.5poise to 300 poise, from 1 poise to 200 poise, and in certainembodiments, from 1 poise to 150 poise, at 25° C. In certainembodiments, an unextended alkenyl-terminated perfluoroether isdifunctional.

In certain embodiments, a hydrosilane-terminated siloxane has thestructure of Formula (2a):

where each R¹ is independently selected from C₁₋₄ alkyl, C₅₋₆cycloalkyl, phenyl, and —O—Si(R²)_(3-m)(H)_(m) or —O—Si(R²)₃, where eachR² is independently C₁₋₄ alkyl, and m is selected from 0, 1, and 2; andn is an integer from 1 to 6.

In certain embodiments of Formula (2a), n is 1, n is 2, n is 3, n is 4,n is 5, and in certain embodiments, n is 6.

In certain embodiments of Formula (2a), each R¹ is independentlyselected from C₁₋₂ alkyl, phenyl, and —O—Si(R²)_(3-m)(H)_(m). In certainembodiments of Formula (2a), each R¹ is independently selected from C₁₋₂alkyl, phenyl, and —O—Si(R²)_(3-m)(H)_(m), where each R² isindependently selected from C₁₋₂ alkyl, and m is selected from 0 and 1.In certain embodiments of Formula (2a), each R¹ is independentlyselected from C₁₋₂ alkyl, phenyl, and —OSi(CH₃)₃. In certain embodimentsof Formula (2a), n is selected from 1 and 2; and each R¹ isindependently selected from C₁₋₂ alkyl, phenyl, and —OSi(CH₃)₃.

In certain embodiments of Formula (2a), each R¹ is independentlyselected from C₁₋₂ alkyl, phenyl, and —OSi(CH₃)₂H and —OSi(CH₃)₃. Incertain embodiments of Formula (2a), n is selected from 1 and 2; andeach R¹ is independently selected from C₁₋₂ alkyl, phenyl, and—OSi(CH₃)₂H and —OSi(CH₃)₃. In certain embodiments, n is selected from 1and 2; and each R¹ is independently selected from —CH₃ and —OSi(CH₃)₂H.

In certain embodiments of a hydrosilane-terminated siloxane of Formula(2a), each R¹ is the same and in certain embodiments, at least one R¹ isdifferent. In certain embodiments, each R¹ is selected from methyl,ethyl, n-propyl, isopropyl, n-butyl, iso-butyl, and tert-butyl. Incertain embodiments, each R¹ is selected from methyl and ethyl. Incertain embodiments, each R¹ is methyl.

In certain embodiments of Formula (2a), when R¹ is—O—Si(R²)_(3-m)(H)_(m), m is 0. In certain embodiments of Formula (2a),when R¹ is —O—Si(R²)_(3-m)(H)_(m), m is 1. In certain embodiments ofFormula (2a), when R¹ is —O—Si(R²)_(3-m)(H)_(m), m is 2.

In certain embodiments of Formula (2a), each R¹ is independentlyselected from C₁₋₄ alkyl, C₅₋₆ cycloalkyl, phenyl, and —O—Si(R²)₃,wherein each R² is independently C₁₋₄ alkyl; and n is an integer from 1to 6.

In certain embodiments, a hydrosilane-terminated siloxane is selectedfrom bis(trimethylsiloxy)-dimethyldisiloxane(bis(1,3,3,3-tetramethyldisiloxanyl)methane) phenyltris(dimethylsiloxy)silane(3-((dimethylsilyl)methyl)-1,1,1,5,5-pentamethyl-3-phenyltrisiloxane),and tetrakis(dimethylsiloxy)silane.

In certain embodiments, a hydrosilane-terminated siloxane isbis(trimethylsiloxy)-dimethyldisiloxane,(bis(1,3,3,3-tetramethyldisiloxanyl)methane), phenyltris(dimethylsiloxy)silane, and in certain embodiments,tetrakis(dimethylsiloxy)silane (Si(—OSi(CH₃)₂H)₄)).

In certain embodiments of Formula (1), -A′- is derived frombis(trimethylsiloxy)-dimethyldisiloxane and has the structure—Si(—CH₃)(—OSi(CH₃)₃)—O—Si(—CH₃)(—OSi(CH₃)₃)—.

In certain embodiments of Formula (1), -A′- is derived from phenyltris(dimethylsiloxy)silane and has the structure—Si(—CH₃)₂—O—Si(-phenyl)(—OSi(—H)(—CH₃)₂—O—Si(—CH₃)₂—.

In certain embodiments, an alkenyl-terminated extended perfluoroether isprepared by reacting an alkenyl-terminated perfluoroether with ahydrosilane-terminated siloxane. In certain embodiments, wherein thealkenyl-terminated perfluoroether is difunctional, the difunctionalalkenyl-terminated perfluoroether may be reacted with a difunctionalhydrosilane-terminated siloxane in an equivalent ratio of about 2:1 toprovide an alkenyl-terminated extended perfluoroether of Formula (1).

Moisture-Curable Compositions

Moisture curing reactions of alkoxysilane-terminated polymers are rapidunder ambient conditions and therefore are useful in aerospace sealantapplications. Thus, modification of perfluoroethers to providealkoxysilane-terminated extended and/or unextended perfluoroethers canprovide polymers useful in high temperature aerospace sealantapplications.

In certain embodiments, a moisture-curable composition comprises analkoxysilane-terminated extended perfluoroether. In certain embodiments,an alkoxysilane-terminated extended perfluoroether comprises acombination of alkoxysilane-terminated extended perfluoroethers. Incertain embodiments, moisture-curable composition comprises one or moreunextended alkoxysilane-terminated perfluoroethers and one or morealkoxy-silane-terminated extended perfluoroethers.

In certain embodiments, an alkoxysilane-terminated extendedperfluoroether comprises a compound of Formula (3):D-CH₂—CH₂-PFE-CH₂—CH₂-A′-CH₂—CH₂-PFE-CH₂—CH₂-D  (3)where each -D is independently —Si(—R³)_(p)(—OR³)_(3-p), where p isindependently selected from 0, 1, and 2; and each R³ is independentlyselected from C₁₋₄ alkyl; -A′- comprises structure moiety of Formula(2b):

where each R¹ is independently selected from C₁₋₄ alkyl, C₅₋₆cycloalkyl, phenyl, and —O—Si(R²)₃, where each R² is independently C₁₋₄alkyl; and n is an integer from 1 to 6; and each —CH₂—CH₂-PFE-CH₂—CH₂—is derived from an alkenyl-terminated perfluoroether, CH₂═CH-PFE-CH═CH₂,where -PFE- comprises perfluoroether groups.

In certain embodiments of Formula (3), -A′- is derived from a siloxaneof Formula (2a). For use in moisture-curable compositions, -A′- does notinclude hydrosilane groups, e.g., is not hydrosilane-terminated.

In certain embodiments of moisture-curable compositions provided by thepresent disclosure, an alkoxysilane-terminated extended perfluoroethercomprises the reaction products of reactants comprising: (a) analkenyl-terminated extended perfluoroether; and (b) an alkoxysilane. Incertain embodiments, the reactants further comprise a catalyst such as ametal catalyst. Examples of suitable metal catalysts formoisture-curable compositions include zinc, tin, and titanium catalystssuch as dibutyltin dioxide, dibutyltin dilaurate, zinc octanoate, andtin octanoate.

In embodiments of the reaction wherein the alkenyl-terminatedperfluoroether is difunctional, e.g., two terminal alkenyl groups, thereactants may be combined in a ratio of alkenyl groups to alkoxysilanegroups of about 1:1, to provide a product having predominately twoterminal alkoxysilane groups such as the alkoxysilane-terminatedextended perfluoroether of Formula (3).

In certain embodiments of the reaction, an alkoxysilane comprises acompound of Formula (4):H—Si(—R³)_(p)(—OR³)_(3-p)  (4)where p is selected from 0, 1, and 2; and each R³ is independentlyselected from C₁₋₄ alkyl.

In certain embodiments of a compound of Formula (4), p is 0, p is 1, andin certain embodiments, p is 2. In certain embodiments of a compound ofFormula (4), each R³ is the same and in certain at least one R³ isdifferent. In certain embodiments, each R³ is independently selectedfrom methyl, ethyl, n-propyl, isopropyl, n-butyl, iso-butyl, andtert-butyl. In certain embodiments, each R³ is independently selectedfrom methyl and ethyl. In certain embodiments, each R³ is methyl.

In certain embodiments of an alkoxysilane of Formula (4), thealkoxysilane is selected from H—Si(—OCH₂CH₃)₃, H—Si(—OCH₃)₃,H—Si(—CH₃)(—OCH₃)₂, H—Si(—CH₃)₂(—OCH₃), H—Si(—CH₃)(—OCH₂CH₃)₂,H—Si(—CH₃)₂(—OCH₂CH₃), H—Si(—CH₂CH₃)(—OCH₃), and H—Si(—CH₂CH₃)₂(—OCH₃).

In certain embodiments of an alkoxysilane of Formula (3), each—Si(—R³)_(p)(—OR³)_(3-p) is selected from —Si(—OCH₂CH₃)₃, —Si(—OCH₃)₃,—Si(—CH₃)(—OCH₃)₂, —Si(—CH₃)₂(—OCH₃), —Si(—CH₃)(—OCH₂CH₃)₂,—Si(—CH₃)₂(—OCH₂CH₃), —Si(—CH₂CH₃)(—OCH₃), and —Si(—CH₂CH₃)₂(—OCH₃). Incertain embodiments, each —Si(—R³)_(p)(—OR³)_(3-p) moiety is—Si(—OCH₂CH₃)₃, —Si(—OCH₃)₃, and in certain embodiments,—Si(—CH₃)(—OCH₃)₂.

In certain embodiments of the reaction, an alkenyl-terminatedperfluoroether comprises a single type of alkenyl-terminatedperfluoroether, and in certain embodiments, a mixture of different typesof alkenyl-terminated perfluoroethers, where the perfluoroethers differ,for example, in molecular weight, perfluoroether backbone, and/or othergroups comprising the backbone.

Examples of suitable alkenyl-terminated perfluoroethers for use in thereaction to provide an alkoxysilane-terminated extended perfluoroetherinclude any of those disclosed herein, such as, for example,alkenyl-terminated perfluoroethers of Formula (1)

In addition to an alkoxysilane-terminated extended perfluoroether,moisture-curable compositions provided by the present disclosure maycomprise an unextended alkoxysilane-terminated perfluoroether includingone or more unextended alkoxysilane-terminated perfluoroethers. Anunextended and/or extended alkoxysilane-terminated perfluoroether maycomprise a combination of alkoxysilane-terminated perfluoroethers havingan average functionality from 2 to 6, such as from 2 to 4, from 2 to 3,and in certain embodiments, from 2 to 2.5.

In certain embodiments, an unextended alkoxysilane-terminatedperfluoroether is difunctional, and in certain embodiments comprises anunextended difunctional alkoxysilane-terminated perfluoroether havingthe structure of Formula (5):D-CH₂—CH₂-PFE-CH₂—CH₂-D  (5)where each D is independently —Si(—R³)_(p)(—OR³)_(3-p), where each p isindependently selected from 0, 1, and 2; and each R³ is independentlyselected from C₁₋₄ alkyl; and —CH₂—CH₂-PFE-CH₂—CH₂— is derived from analkenyl-terminated perfluoroether CH₂═CH-PFE-CH═CH₂, wherein -PFE-comprises polythioether groups.

In certain embodiments, an unextended alkoxysilane-terminatedperfluoroether comprises the reaction products of reactants comprisingan unextended alkenyl-terminated perfluoroether; and an alkoxysilane.

In certain embodiments of the reaction, an alkenyl-terminatedperfluoroether comprises a perfluoroether group selected from—[—CF₂—CF₂—CF₂—O—]_(k)—, —CF₂—O—[—CF₂—CF₂—O—]_(k)—[—CF₂—O—]_(k)—CF₂—,—[—CF(CF₃)—CF₂—O—]_(k)—, —[—CF₂—CF(CF₃)—O—]_(k)—, and a combination ofany of the foregoing, and in certain embodiments, each k is 2 to 100.

In certain embodiments of an unextended difunctionalalkoxysilane-terminated perfluoroether of Formula (5), each p is 0, eachp is 1, and in certain embodiments, each p is 2. In certain embodimentsof a compound of Formula (5), each R³ is selected from ethyl and methyl,in certain embodiments, each R³ is ethyl, and in certain embodiments,each R³ is methyl.

In certain embodiments, a moisture-curable composition comprises thereaction products of reactants comprising: (a) an unextendedalkenyl-terminated perfluoroether; (b) a hydrosilane-terminatedsiloxane; and (c) an alkoxysilane.

In certain embodiments of the reaction, the unextendedalkenyl-terminated perfluoroether (a) comprises perfluoroether groupsselected from —[—CF₂—CF₂—CF₂—O—]_(k)—,—CF₂—O—[—CF₂—CF₂—O—]_(k)—[—CF₂—O—]_(k)—CF₂—, —[—CF(CF₃)—CF₂—O—]_(k)—,—[—CF₂—CF(CF₃)—O—]_(k)—, and a combination of any of the foregoing,wherein each k is independently an integer from 2 to 100.

In certain embodiments of the reaction, the hydrosilane-terminatedsiloxane (b) comprises a compound of Formula (2a):

wherein each R¹ is independently selected from C₁₋₄ alkyl, C₅₋₆cycloalkyl, phenyl, and —O—Si(R²)₃, wherein each R² is independentlyC₁₋₄ alkyl; and n is an integer from 1 to 6.

In certain embodiments, a moisture-curable composition comprises thereaction products of reactants comprising:

(a) an alkenyl-terminated perfluoroether comprising a perfluoroethergroup selected from —[—CF₂—CF₂—CF₂—O—]_(k)—,—CF₂—O—[—CF₂—CF₂—O—]_(k)—[—CF₂—O—]_(k)—CF₂—, —[—CF(CF₃)—CF₂—O—]_(k)—,—[—CF₂—CF(CF₃)—O—]_(k)—, and a combination of any of the foregoing, andin certain embodiments, k is 2 to 100;

(b) a hydrosilane-terminated siloxane of Formula (2a):

where each R¹ is independently selected from C₁₋₄ alkyl, C₅₋₆cycloalkyl, phenyl, and —O—Si(R²)₃, where each R² is independently C₁₋₄alkyl; and n is an integer from 1 to 6; and

(c) an alkoxysilane of Formula (4):H—Si(—R³)_(p)(—OR³)_(3-p)  (4)where p is selected from 0, 1, and 2; and each R³ is independentlyselected from C₁₋₄ alkyl.

In certain embodiments, a moisture-curable composition may be preparedby steps comprising: (a) reacting an unextended alkenyl-terminatedperfluoroether and a hydrosilane-terminated siloxane to provide amixture of alkenyl-terminated extended perfluoroethers and unextendedalkenyl-terminated perfluoroethers; and (b) reacting the mixture with analkoxysilane to provide a mixture of alkoxysilane-terminated extendedperfluoroethers and unextended alkoxysilane-terminated perfluoroethers.

In certain embodiments, an unextended alkenyl-terminated perfluoroetherand a hydrosilane-terminated siloxane are reacted in an equivalent ratiofrom 8:1 to 2:1; from 6:1 to 2.5:1; from 5:1 to 3:1, and in certainembodiments, 4:1.

In certain embodiments, a moisture-curable composition may be preparedby first reacting a difunctional alkenyl-terminated perfluoroether and adifunctional hydrosilane-terminated siloxane in an equivalent ratio of4:1 to provide a partially extended perfluoroether meaning that theresulting perfluoroether comprises a mixture of the difunctionalalkenyl-terminated perfluoroether and a difunctional alkenyl-terminatedextended perfluoroether, such as a mixture of 1:1. In a second step, themixture of alkenyl-terminated extended and unextended perfluoroethersmay be reacted with an alkoxysilane in the presence, for example, of aplatinum catalyst, to provide a mixture of alkoxysilane-terminatedextended and unextended perfluoroethers. In certain embodiments, anextended alkoxysilane-terminated perfluoroether comprises the reactionproducts of reactants comprising: (a) an alkenyl-terminatedperfluoroether; and (b) a hydro silane-terminated siloxane.

In certain embodiments of the preceding reaction, the reaction productscomprise an alkoxysilane-terminated extended perfluoroether, and incertain embodiments, a mixture of an unextended alkoxysilane-terminatedperfluoroether and an alkoxysilane-terminated extended perfluoroether.

For moisture-curable compositions it is desirable that thealkenyl-terminated extended perfluoroether not contain any orsubstantially any reactive hydrosilane groups. This may be accomplishedby reacting appropriate equivalent ratios of alkenyl and hydrosilanegroups.

In certain embodiments of moisture-curable compositions, ahydrosilane-terminated siloxane has the structure of Formula (2a):

where each R¹ is independently selected from C₁₋₄ alkyl, C₅₋₆cycloalkyl, phenyl, and —O—Si(R²)₃, where each R² is independently C₁₋₄alkyl; and n is an integer from 1 to 6.

In certain embodiments of Formula (2a), n is 1, n is 2, n is 3, n is 4,n is 5, and in certain embodiments, n is 6.

In certain embodiments of Formula (2a), each R¹ is independentlyselected from methyl, ethyl, phenyl, and —Si(R²)₃. In certainembodiments, each R¹ is independently selected from methyl, ethyl, andphenyl. In certain embodiments, each R¹ is independently selected frommethyl and phenyl. In certain embodiments, each R¹ is independentlyselected from methyl, phenyl, and —Si(R²)₃. In certain embodiments, eachR¹ is independently selected from methyl, ethyl, n-propyl, isopropyl,n-butyl, isobutyl, and tert-butyl. In certain embodiments, each R¹ ismethyl.

In certain embodiments of —Si(R²)₃, each R² is independently selectedfrom methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, andtert-butyl. In certain embodiments, each R² is independently selectedfrom methyl and ethyl, in certain embodiments, each R² is ethyl, and incertain embodiments, each R² is methyl.

In certain embodiments, a partially extended perfluoroether may beprepared, where partial extension refers to a reaction product of analkenyl-terminated perfluoroether with a hydrosilane-terminated siloxanesuch that the product comprises a combination of extendedperfluoroethers and non-extended perfluoroethers. For example, thereaction of a difunctional alkenyl-terminated perfluoroether with adifunctional hydrosilane-terminated siloxane in an equivalent ration of2:<1, such as 2:0.8, 2:0.6, 2:0.5, 2:0.4 or 2:0.2, providespredominately a mixture of extended and unextended alkenyl-terminatedperfluoroethers.

An alkenyl-terminated perfluoroether may then be capped or terminatedwith an alkoxysilane such as —O—Si(—OR²)₃, including, for example,trimethoxysilane, or triethoxysilane to provide analkoxysilane-terminated perfluoroether, which, in certain embodiments,may be a combination of alkoxysilane-terminated extended perfluoroethersand unextended alkoxysilane-terminated perfluoroethers.

In certain embodiments, an alkoxysilane-terminated perfluoroethercomprises a perfluoroether of Formula (3), a perfluoroether of Formula(5), and in certain embodiments, a mixture of an alkoxysilane-terminatedextended perfluoroether of Formula (3) and an unextendedalkoxysilane-terminated perfluoroether of Formula (5).

Uncured compositions comprising a combination of alkoxysilane-terminatedextended perfluoroethers and unextended alkoxysilane-terminatedperfluoroethers, e.g., partially extended alkoxy-terminatedperfluoroethers, may be viscous pastes at room temperature and, whenmoisture-cured, exhibit high thermal resistance and other propertiesuseful in aerospace sealant applications.

Addition-Curable Compositions

In certain embodiments of the present disclosure, addition-curablecompositions are provided. Addition-curable compositions provided by thepresent disclosure may be cured by the reaction of perfluoroethershaving terminal alkenyl groups, —CH═CH₂ (alkenyl-terminatedperfluoroethers), with perfluoroethers having terminal hydrosilanegroups, —Si(R)₂H (hydrosilane-terminated perfluoroethers), in thepresence of a metal catalyst.

In general, addition-curable compositions comprise an alkenyl-terminatedperfluoroether or mixture of alkenyl-terminated perfluoroethers, and ahydrosilane-terminated perfluoroether or a mixture ofhydrosilane-terminated perfluoroethers. An alkenyl-terminatedperfluoroether may comprise any of those disclosed herein. Ahydrosilane-terminated perfluoroether may be similar to thealkoxysilane-terminated perfluoroethers disclosed herein, except thatthe perfluoroether is terminated with one or more hydrosilane groups.

In certain embodiments of addition-curable compositions, analkenyl-terminated perfluoroether may be extended and/or unextended, anda hydrosilane-terminated perfluoroether may be extended and/orunextended.

In certain embodiments, an addition-curable composition comprises one ormore unextended alkenyl-terminated perfluoroethers and a combination ofextended and unextended hydrosilane-terminated perfluoroethers having anaverage functionality from 2 to 6, from 3 to 6, from 4 to 6, from 3 to5, and in certain embodiments, from 4 to 5.

In certain embodiments of an addition-curable composition, theequivalent ratio of terminal alkenyl groups to terminal hydrosilanegroups from 0.5:1 to 1.5:1, from 0.75:1 to 1.25:1, from 0.8:1 to 1.2:1,from 0.9:1 to 1.1:1, from 0.95:1 to 1.05:1, and in certain embodiments,is 1:1.

In certain embodiments, addition-curable compositions comprise (a) analkenyl-terminated perfluoroether, and (b) a hydrosilane-terminatedextended perfluoroether.

In certain embodiments, an alkenyl-terminated perfluoroether comprises asingle type of alkenyl-terminated perfluoroether or a combination ofalkenyl-terminated perfluoroethers. An alkenyl-terminated perfluoroethermay comprise any of the unextended alkenyl-terminated perfluoroethersdisclosed herein, such as for example, an unextended alkenyl-terminatedperfluoroether of the formula CH₂═CH-PFE-CH═CH₂, or combinationsthereof. In certain embodiments, an alkenyl-terminated perfluoroethermay be a difunctional unextended alkenyl-terminated perfluoroether. Incertain embodiments, an alkenyl-terminated perfluoroether comprises analkenyl-terminated extended perfluoroether or combination ofalkenyl-terminated extended perfluoroethers including any of thosedisclosed herein such as, for example, an alkenyl-terminated extendedperfluoroether of Formula (1). In certain embodiments, analkenyl-terminated perfluoroether may be a difunctionalalkenyl-terminated extended perfluoroether. In certain embodiments, analkenyl-terminated perfluoroether comprises a combination of unextendedalkenyl-terminated perfluoroethers and alkenyl-terminated extendedperfluoroethers. In certain embodiments, an alkenyl-terminatedperfluoroether comprises a combination of unextended difunctionalalkenyl-terminated perfluoroethers and difunctional alkenyl-terminatedextended perfluoroethers.

Hydrosilane-terminated perfluoroethers useful in addition-curablecompositions include difunctional hydrosilane-terminatedperfluoroethers, hydrosilane-terminated perfluoroethers having afunctionality greater than 2, and combinations thereof. Hydrosilane-terminated perfluoroethers may be unextended hydrosilane-terminated perfluoroethers, hydro silane-terminated extendedperfluoroethers, or combinations thereof.

In certain embodiments, an addition-curable composition comprises ahydrosilane-terminated perfluoroether having the structure of Formula(8):A-CH₂—CH₂-PFE-CH₂—CH₂-A  (8)where each A- is independently selected from a moiety of Formula (2c)and Formula (10b):

where each R¹ is independently selected from C₁₋₄ alkyl, C₅₋₆cycloalkyl, phenyl, and —O—Si(R²)_(3-m)(H)_(m) where each R² isindependently C₁₋₄ alkyl, m is selected from 0, 1, and 2; n is aninteger from 1 to 6; and —CH₂—CH₂-PFE-CH₂—CH₂— is derived from adialkenyl-terminated perfluoroether of the formula CH₂═CH-PFE-CH═CH₂where -PFE- comprises perfluoroether groups.

In certain embodiments, an addition-curable composition comprises ahydro silane-terminated extended perfluoroether having the structure ofFormula (9);A-CH₂—CH₂-PFE-CH₂—CH₂-A′-CH₂—CH₂-PFE-CH₂—CH₂-A  (9)where each A- is independently a group of Formula (2c):

where each R¹ is independently selected from C₁₋₄ alkyl, C₅₋₆cycloalkyl, phenyl, and —O—Si(R²)_(3-m)(H)_(m) where each R² isindependently C₁₋₄ alkyl; and m is selected from 0, 1, and 2; n is aninteger from 1 to 6; and -A′- is a group of Formula (2c):

where each R¹ is independently selected from C₁₋₄ alkyl, C₅₋₆cycloalkyl, phenyl, and —O—Si(R²)_(3-m)(H)_(m) where each R² isindependently C₁₋₄ alkyl; and m is selected from 0, 1, and 2; and n isan integer from 1 to 6; and —CH₂—CH₂-PFE-CH₂—CH₂— is derived from adialkenyl-terminated perfluoroether CH₂═CH-PFE-CH═CH₂ wherein -PFE-comprises perfluoroether groups.

In perfluoroethers of Formula (8) and Formula (9), the moiety—CH₂—CH₂-PFE-CH₂—CH₂— may be derived from a difunctionalalkenyl-terminated perfluoroether having the structureCH₂═CH-PFE-CH═CH₂; and each -A and -A′- are derived from ahydrosilane-terminated siloxane.

In certain embodiments of Formula (8) and Formula (9), -PFE- comprisesperfluoroether groups selected from —[—CF₂—CF₂—CF₂—O—]_(k)—,—CF₂—O—[—CF₂—CF₂—O—]_(k)—[—CF₂—O—]_(k)—CF₂—, —[—CF(CF₃)—CF₂—O—]_(k)—,—[—CF₂—CF(CF₃)—O—]_(k)—, and a combination of any of the foregoing,wherein each k is independently an integer from 2 to 100.

Hydrosilane-terminated perfluoroethers provided by the presentdisclosure may be prepared by reacting an alkenyl-terminatedperfluoroether, such as a difunctional alkenyl-terminatedperfluoroether, with a hydrosilane-terminated siloxane. Thealkenyl-terminated perfluoroether and the hydro silane-terminatedsiloxane may be any of those disclosed herein. In certain embodiments,the alkenyl-terminated perfluoroether has the structureCH₂═CH-PFE-CH═CH₂ and the hydrosilane-terminated siloxane has thestructure of Formula (2a).

In certain embodiments, an addition-curable composition comprises acombination of hydrosilane-terminated perfluoroethers of Formula (8) andFormula (9). In certain embodiments, an addition-curable compositioncomprises a combination of alkenyl-terminated extended perfluoroethersof Formula (1) and in certain embodiments, of the formulaCH₂═CH-PFE-CH═CH₂.

In certain embodiments, when used as a terminal group, and not as anextending group, a hydrosilane-terminated siloxane may be selected frombis(trimethylsiloxy)-dimethyldisiloxane, phenyltris(dimethylsiloxy)silane, teteramethylcyclotetrasiloxane(bis(trimethylsiloxy)-dimethylsiloxane(1,1,1,3,5,7,7,7-octamethyltetrasiloxane, TMCTS), andtetrakis(dimethylsiloxy)silane (Si—(—OSiMe₂H)₄).

In certain embodiments of Formula (8) and Formula (9), each -A isderived from bis(trimethylsiloxy)-dimethylsiloxane(1,1,1,3,5,7,7,7-octamethyltetrasiloxane), and each -A has thestructure:

and the corresponding compound of Formula (8) and/or Formula (9) is ahydrosilane-terminated perfluoroether having at least two reactivehydrosilane functionalities. Depending on whether the siloxane used asan extending group includes hydrosilane groups, the correspondingcompound of Formula (8) and/or Formula (9) may have more than tworeactive hydrosilane functionalities.

In certain embodiments of compounds of Formula (8) and Formula (9), each-A is derived from phenyl tris(dimethylsiloxy)silane(3-((dimethylsilyl)oxy)-1,2,5,5-tetramethyl-3-phenyltrisiloxane), andeach -A has the structure:

and the corresponding compound of Formula (8) and/or Formula (9) is ahydrosilane-terminated perfluoroether having at least four reactivehydrosilane functionalities. Depending on whether the siloxane used asan extending group includes hydrosilane groups, the correspondingcompound of Formula (8) and/or Formula (9) may have more than fourreactive hydrosilane functionalities.

In certain embodiments, each -A is derived from is derived fromtetramethylcyclotetrasiloxane(2,4,6,8-tetramethyl-1,3,5,7,2,4,6,8-tetraoxatetrasilocane)(TMCTS), and each -A has the structure:

and the corresponding compound of Formula (8) and/or Formula (9) is ahydrosilane-terminated perfluoroether having at least six reactivehydrosilane functionalities. Depending on whether the siloxane used asan extending group includes hydrosilane groups, the correspondingcompound of Formula (8) and/or Formula (9) may have more than sixreactive hydrosilane functionalities.

In certain embodiments, -A is derived fromtetrakis(dimethylsiloxy)silane, and each -A has the structure:

and the corresponding compound of Formula (8) and/or Formula (9) is ahydrosilane-terminated perfluoroether having at least six reactivehydrosilane functionalities. Depending on whether the siloxane used asan extending group includes hydrosilane groups, the correspondingcompound of Formula (8) and/or Formula (9) may have more than sixreactive hydrosilane functionalities. In certain embodiments of Formula(8) and Formula (9), each A- isSi(CH₃)₂H—O—Si(—O—Si(CH₃)₂H)₂—O—Si(CH₃)₂—.

As indicated, polyfunctional hydrosilane-terminated perfluoroethers mayalso be prepared by extension using a hydrosilane-terminated siloxane asan extender followed by capping with a hydrosilane-terminated siloxane.This may be accomplished in a two-step process comprising extensionfollowed by capping or termination, or in a single reaction step. Suchreactions can produce hydrosilane-terminated perfluoroethers havingvarious hydrosilane functionalities, with the predominant or averagefunctionality determined by the equivalent ratio of the reactants.

For example, as shown in Scheme 1, a difunctional hydrosilane-terminatedperfluoroether may be prepared by reacting a difunctionalalkenyl-terminated perfluoroether andbis(trimethylsiloxy)-dimethylsiloxane in the presence of a catalyst,such as a platinum catalyst, to provide an unextended difunctionalhydrosilane-terminated perfluoroether.

As shown in Scheme 2, a tetrafunctional hydrosilane-terminatedperfluoroether may be prepared by reacting a difunctionalalkenyl-terminated perfluoroether and phenyl tris(dimethylsiloxy)silanein the presence of a catalyst, such as a platinum catalyst, to providean unextended tetrafunctional hydro silane-terminated perfluoroether.

As shown in Scheme 3, a pentafunctional hydrosilane-terminatedperfluoroether may be prepared by reacting a difunctionalalkenyl-terminated perfluoroether and phenyl tris(dimethylsiloxy)silanein the presence of a catalyst such as a platinum catalyst, to provide apentafunctional hydrosilane-terminated extended perfluoroether in whichthe extending group has a single hydrosilane group, and phenyltris(dimethylsiloxy)silane terminal groups.

In certain embodiments, the alkenyl-terminated perfluoroether is adifunctional alkenyl-terminated perfluoroether, which may be unextended,extended, or a combination thereof.

In certain embodiments, an extended and/or unextendedhydrosilane-terminated perfluoroether comprises two hydrosilanefunctionalities, in certain embodiments, three hydrosilanefunctionalities, four hydrosilane functionalities, five hydrosilanefunctionalities, six hydrosilane functionalities, and in certainembodiments, more than six hydrosilane functionalities. Anaddition-curable composition provided by the present disclosure maycomprise a combination of extended and/or unextendedhydrosilane-terminated perfluoroethers having two hydrosilane terminalgroups, three, four, five, six, more than six hydrosilane terminalgroups, or a combination of any of the foregoing.

For example, a sealant provided by the present disclosure may comprise adifunctional alkenyl-terminated perfluoroether, a tetrafunctionalhydrosilane-terminated perfluoroether of Formula (9), and apentafunctional hydrosilane-terminated perfluoroether of Formula (9), inan equivalent ratio of 1:0.5:0.5, respectively.

As another example, a sealant provided by the present disclosure maycomprise a difunctional alkenyl-terminated perfluoroether, adifunctional hydrosilane-terminated perfluoroether, a tetrafunctionalhydrosilane-terminated perfluoroether of Formula (9), and ahexafunctional hydrosilane-terminated perfluoroether of Formula (9), inan equivalent ratio of 1:0.15:0.7:0.15, respectively.

Suitable catalysts for use in the reaction of an alkenyl-terminatedperfluoroether with an hydrosilane-terminated siloxane include Speier'scatalyst (hexachloroplatinic acid H₂PtCl₆) and Karstedt catalyst (acomplex of platinum with divinyltetramethyldisiloxane).

Sealants

Alkoxysilane-terminated perfluoroethers provided by the presentdisclosure are useful in moisture-curable compositions, such as coatingsand sealant compositions, including those that may be employed asaerospace sealants and as linings for fuel tanks. As a result, certainembodiments provided by the present disclosure are directed tocompositions, such as one-part compositions, that include analkoxysilane-terminated perfluoroether and a curing agent. In theseone-part compositions, an alkoxysilane-terminated perfluoroether andcuring agent, optionally in combination with other compositioncomponents, are combined and packaged in a single, moisture-sealed, suchas vacuum-sealed or sealed with an inert gas, container to substantiallyprevent curing prior to use. The compositions are stable at ambienttemperatures under conditions substantially free of moisture. Free ofmoisture and substantially free of moisture means that, although acomposition may contain some moisture, the amount of moisture is notsufficient to substantially effect curing of the composition. When acomposition is exposed to sufficient moisture, curing of the compositionis promoted to form a sealant useful in many applications, including,for example, aerospace and similar applications.

Addition-curable compositions comprising hydrosilane-terminatedperfluoroethers provided by the present disclosure are typicallytwo-part systems. In certain embodiments, such compositions, includingsealants, may be provided as multi-part compositions, such as two-partcompositions, wherein one part comprises one or morehydrosilane-terminated perfluoroethers provided by the presentdisclosure and a second part comprises one or more alkenyl-terminatedperfluoroethers provided by the present disclosure. Additives and/orother materials may be added to either part as desired or as necessary.The two parts may be combined and mixed prior to use. In certainembodiments, the pot life of the mixed composition is at least 30minutes, at least 1 hour, at least 2 hours, and in certain embodiments,more than 2 hours, where pot life refers to the period of time the mixedcomposition remains suitable for application as a sealant after mixing.A hydrosilylation catalyst, such as a platinum catalyst, may be includedin either part, or may be included in a third part and combined prior toapplication.

In certain embodiments, alkoxysilane-terminated perfluoroethers andhydrosilane-terminated perfluoroethers provided by the presentdisclosure may be present in a composition in an amount from 30 wt % to90 wt %, such as from 40 wt % to 80 wt %, or, in certain embodiments,from 45 wt % to 75 wt %, where wt % is based on the total weight of allnon-volatile components of the composition.

In certain embodiments, compositions may comprise one or more adhesionpromoters. An adhesion promoter may be present in amount from 0.1 wt %to 15 wt % of a composition, less than 5 wt %, less than 2 wt %, and incertain embodiments, less than 1 wt %, based on the total dry weight ofthe composition. Examples of adhesion promoters include phenolics, suchas Methylon® phenolic resin, and organosilanes, such as epoxy-,mercapto-, or amino-terminated silanes, such as Silquest® A-187 andSilquest® A-1100. Other useful adhesion promoters are known in the art.Compositions may comprise a sulfur-containing adhesion promoter asdisclosed in U.S. application Ser. No. 13/529,183 filed on Jun. 21,2012.

Compositions provided by the present disclosure may comprise one or moredifferent types of filler. Suitable fillers include those commonly knownin the art, including inorganic fillers, such as carbon black andcalcium carbonate (CaCO₃), silica, metal oxide, polymer powders, andlightweight fillers. Suitable lightweight fillers include, for example,those described in U.S. Pat. No. 6,525,168. In certain embodiments, acomposition includes 5 wt % to 60 wt % of the filler or combination offillers, 10 wt % to 50 wt %, and in certain embodiments, from 20 wt % to40 wt %, based on the total dry weight of the composition. Compositionsprovided by the present disclosure may further include one or morecolorants, pigments, plasticizers, surfactants, thixotropic agents,accelerators such as amines, including 1,4-diaza-bicyclo[2.2.2]octane,fire retardants, adhesion promoters, solvents, masking agents, or acombination of any of the foregoing. In certain embodiments ofcompositions provided by the present disclosure, a basic oxide ispresent in an amount of 0.1 wt % to 10 wt %, such as 1 wt % to 10 wt %,or, in certain embodiments, 5 wt % to 10 wt %, based on the total weightof the composition. As can be appreciated, fillers and additivesemployed in a composition may be selected so as to be compatible witheach other as well as the polymeric component, curing agent, and orcatalyst.

In certain embodiments, compositions provided by the present disclosurecomprise a basic oxide. Basic oxides may be particularly useful inmoisture-curable compositions where they may act as dehydrating agents,thereby preventing premature cure of the composition, but when cure isdesired, the base that is generated acts as a curing catalyst. As aresult, it is possible to use less cure accelerator, such as an amine,in moisture-curable compositions e, which may further extend theshelf-life of the compositions. Examples of basic oxides suitable foruse in compositions provided by the present disclosure include calciumoxide, magnesium oxide, barium oxide, or a combination of any of theforegoing. In certain embodiments of compositions provided by thepresent disclosure, a basic oxide is present in an amount of 0.1 wt % to10 wt %, such as 1 wt % to 10 wt %, or, in certain embodiments, 5 wt %to 10 wt %, based on the total weight of the composition.

In certain embodiments, moisture-curable compositions include a tincatalyst. Examples of suitable tin catalysts include organo tincompounds such as aliphatic titiantes including dibutyltin oxide,dibutyltin bis(acetylacetonate), dibutyltin dilaurate, dibutyltindiacetate, tetrabutyl titanate, and tetraethyltitanate.

In certain embodiments, addition-curable compositions provided by thepresent disclosure comprise a platinum catalyst. Examples of suitableplatinum catalysts include Speier's catalyst and Karstedt catalyst.

In certain embodiments, compositions provided by the present disclosurecomprise electrically conductive filler. Electrical conductivity andEMI/RFI shielding effectiveness can be imparted to a composition byincorporating conductive materials. Conductive elements can include, forexample, metal or metal-plated particles, fabrics, meshes, fibers, andcombinations of any of the foregoing. The metal may be in the form of,for example, filaments, particles, flakes, or spheres. Examples ofmetals include copper, nickel, silver, aluminum, tin, and steel. Otherconductive materials that can be used to impart EMI/RFI shieldingeffectiveness to polymer compositions include conductive particles orfibers comprising carbon or graphite. In certain embodiments, acomposition comprises at least about 20 wt % and in certain embodiments,at least about 30 wt % of an electrically conductive filler.

Fillers used to impart electrical conductivity and EMI/RFI shieldingeffectiveness to polymer compositions are well known in the art.Examples of electrically conductive fillers include electricallyconductive noble metal-based fillers such as pure silver; noblemetal-plated noble metals such as silver-plated gold; noble metal-platednon-noble metals such as silver plated cooper, nickel or aluminum, forexample, silver-plated aluminum core particles or platinum-plated copperparticles; noble-metal plated glass, plastic or ceramics such assilver-plated glass microspheres, noble-metal plated aluminum ornoble-metal plated plastic microspheres; noble-metal plated mica; andother such noble-metal conductive fillers. Non-noble metal-basedmaterials can also be used and include, for example, non-noblemetal-plated non-noble metals such as copper-coated iron particles ornickel plated copper; non-noble metals, e.g., copper, aluminum, nickel,cobalt; non-noble-metal-plated-non-metals, e.g., nickel-plated graphiteand non-metal materials such as carbon black and graphite. Combinationsof electrically conductive fillers can also be used to meet the desiredconductivity, EMI/RFI shielding effectiveness, hardness, and otherproperties suitable for a particular application.

The shape and size of an electrically conductive filler used in acomposition provided by the present disclosure may be any appropriateshape and size to impart EMI/RFI shielding effectiveness to the curedcomposition. For example, fillers can be of any shape that is generallyused in the manufacture of electrically conductive fillers, includingspherical, flake, platelet, particle, powder, irregular, fiber, and thelike. In certain compositions provided by the disclosure, a basecomposition can comprise Ni-coated graphite as a particle, powder orflake. In certain embodiments, the amount of Ni-coated graphite in abase composition can range from 40 wt % to 80 wt %, and in certainembodiments can range from 50 wt % to 70 wt %, based on the total weightof the base composition. In certain embodiments, electrically conductivefiller can comprise nickel fiber. Nickel fiber can have a diameterranging from 10 μm to 50 μm and have a length ranging from 250 μm to 750μm. A base composition can comprise, for example, an amount of nickelfiber ranging from 2 wt % to 10 wt %, and in certain embodiments, from 4wt % to 8 wt %, based on the total weight of the base composition.

Carbon fibers, particularly graphitized carbon fibers, may also be usedto impart electrical conductivity to a composition provided by thepresent disclosure. Carbon fibers formed by vapor phase pyrolysismethods and graphitized by heat treatment and which are hollow or solidwith a fiber diameter ranging from 0.1 micron to several microns, havehigh electrical conductivity. As disclosed in U.S. Pat. No. 6,184,280,carbon microfibers, nanotubes or carbon fibrils having an outer diameterof less than 0.1 micron to tens of nanometers can be used aselectrically conductive fillers.

The average particle size of electrically conductive filler may bewithin a range useful for imparting electrical conductivity to acomposition. For example, in certain embodiments, the particle size ofthe one or more fillers can range from 0.25 μm to 250 μm, in certainembodiments can range from 0.25 μm to 75 μm, and in certain embodimentscan range from 0.25 μm to 60 μm.

In certain embodiments, electrically conductive polymers may be used toimpart or modify the electrical conductivity of a composition providedby the present disclosure. Polymers having sulfur atoms incorporatedinto aromatic groups or adjacent to double bonds, such as inpolyphenylene sulfide, and polythiophene, are known to be electricallyconductive. Other electrically conductive polymers include, for example,polypyrroles, polyaniline, poly(p-phenylene) vinylene, andpolyacetylene. Compositions provided by the present disclosure cancomprise more than one electrically conductive filler, and the more thanone electrically conductive filler can be of the same or differentmaterials and/or shapes. For example, a sealant composition may compriseelectrically conductive Ni fibers, and electrically conductive Ni-coatedgraphite in the form of powder, particles or flakes. The amount and typeof electrically conductive filler can be selected to produce a sealantcomposition which, when cured, exhibits a sheet resistance (four-pointresistance) of less than 0.50Ω·/cm², and in certain embodiments, a sheetresistance of less than 0.15 Ω/cm². The amount and type of filler canalso be selected to provide effective EMI/RFI shielding over a frequencyrange of from 1 MHz to 18 GHz for an aperture sealed using a sealantcomposition provided by the present disclosure.

Galvanic corrosion of dissimilar metal surfaces and the conductivecompositions of the present disclosure can be minimized or prevented byadding corrosion inhibitors to the composition, and/or by selectingappropriate conductive fillers. In certain embodiments, corrosioninhibitors include strontium chromate, calcium chromate, magnesiumchromate, and combinations thereof. U.S. Pat. No. 5,284,888 and U.S.Pat. No. 5,270,364 disclose the use of aromatic triazoles to inhibitcorrosion of aluminum and steel surfaces. In certain embodiments, asacrificial oxygen scavenger such as Zn can be used as a corrosioninhibitor. In certain embodiments, a corrosion inhibitor can compriseless than 10% by weight of the total weight of the electricallyconductive composition. In certain embodiments, a corrosion inhibitorcan comprise an amount ranging from 2% by weight to 8% by weight of thetotal weight of the electrically conductive composition. Corrosionbetween dissimilar metal surfaces may also be minimized or prevented bythe selection of the type, amount, and properties of the conductivefillers comprising the composition.

Uses

Compositions provided by the present disclosure may be used, forexample, in sealants, coatings, encapsulants, and potting compositions.A sealant includes a composition capable of producing a film that hasthe ability to resist operational conditions, such as moisture andtemperature, and at least partially block the transmission of materials,such as water, fuel, and other liquid and gases. A coating compositionincludes a covering that is applied to the surface of a substrate to,for example, improve the properties of the substrate such as theappearance, adhesion, wettability, corrosion resistance, wearresistance, fuel resistance, and/or abrasion resistance. A pottingcomposition includes a material useful in an electronic assembly toprovide resistance to shock and vibration and to exclude moisture andcorrosive agents. In certain embodiments, sealant compositions providedby the present disclosure are useful, e.g., as aerospace sealants and aslinings for fuel tanks.

Compositions, including sealants, provided by the present disclosure maybe applied to any of a variety of substrates. Examples of substrates towhich a composition may be applied include metals such as titanium,stainless steel, and aluminum, any of which may be anodized, primed,organic-coated or chromate-coated; epoxy; urethane; graphite; fiberglasscomposite; Kevlar®; acrylics; and polycarbonates. In certainembodiments, compositions provided by the present disclosure may beapplied to a coating on a substrate, such as a polyurethane coating.

Compositions provided by the present disclosure may be applied directlyonto the surface of a substrate or over an underlayer by any suitablecoating process known to those skilled in the art.

Compositions provided by the present disclosure may be applied directlyonto the surface of a substrate or over an underlayer or a coating byany suitable coating process known to those skilled in the art.

Furthermore, methods are provided for sealing an aperture utilizing acomposition provided by the present disclosure. These methods comprise,for example, applying a composition provided by the present disclosureto a surface to seal an aperture, and curing the composition. In certainembodiments, a composition may be cured under ambient conditions, whereambient conditions refers to a temperature from 20° C. to 25° C., andatmospheric humidity. In certain embodiments, a composition may be curedunder conditions encompassing a temperature from a 0° C. to 100° C. anda humidity from 0% RH to 100% RH (or in the case of a moisture-curablecomposition, at a humidity greater than 0% RH). In certain embodiments,a composition may be cured at a higher temperature such as at least 30°C., at least 40° C., and in certain embodiments, at least 50° C. Incertain embodiments, a composition may be cured at room temperature,e.g., 25° C. In certain embodiments, a composition may be cured uponexposure to actinic radiation such as ultraviolet radiation. As willalso be appreciated, the methods may be used to seal apertures onaerospace vehicles including aircraft and aerospace vehicles.

In certain embodiments, for storage and transportation, the compositioncomponents, including an alkoxysilane-terminated perfluoroether andcuring agent, are combined in a container and sealed from moisture.While sealed from moisture in the container, the moisture-curablecomposition is stable and remains substantially uncured for an extendedtime period.

For addition-curable compositions, the two-parts may be mixed prior touse and applied to the substrate as long as the mixed components remainworkable. Addition curable compositions include a hydrosilylationcatalyst such as a platinum catalyst in the olefin-containing part, thesilyl-containing part, or may be included in a third part and combinedwith the first and second parts prior to application.

When exposed to the moisture in air, the components of moisture-curablecompositions provided by the present disclosure react to provide curedcompositions, including sealant compositions.

In certain embodiments, a composition provided by the present disclosureachieves a tack-free cure in less than about 2 hours, less than about 4hours, less than about 7 hours, and in certain embodiments, less thanabout 10 hours at a temperature of less than about 200° F.

Cured compositions such as cured sealants exhibit properties acceptablefor use in aerospace applications. In general, it is desirable thatsealants used in aviation and aerospace applications exhibit thefollowing properties: peel strength greater than 20 pounds per linearinch (pli) on Aerospace Material Specification (AMS) 3265B substratesdetermined under dry conditions, following immersion in JRF for 7 days,and following immersion in a solution of 3% NaCl according to AMS 3265Btest specifications; tensile strength between 300 pounds per square inch(psi) and 400 psi; tear strength greater than 50 pounds per linear inch(pli); elongation between 250% and 300%; and hardness greater than 40Durometer A. These and other cured sealant properties appropriate foraviation and aerospace applications are disclosed in AMS 3265B, theentirety of which is incorporated herein by reference. It is alsodesirable that when cured, curable compositions of the presentdisclosure used in aviation and aircraft applications exhibit a percentvolume swell not greater than 25% following immersion for one week at60° C. (140° F.) and ambient pressure in Jet Reference Fuel Type I (JRFType I). Other properties, ranges, and/or thresholds may be appropriatefor other sealant applications.

In certain embodiments, compositions provided by the present disclosureare fuel-resistant. As used herein, the term “fuel resistant” means thata composition, when applied to a substrate and cured, can provide acured product, such as a sealant, that exhibits a percent volume swellof not greater than 40%, in some cases not greater than 25%, in somecases not greater than 20%, in yet other cases not more than 10%, afterimmersion for one week at 140° F. (60° C.) and ambient pressure in JRFType I according to methods similar to those described in ASTM D792(American Society for Testing and Materials) or AMS 3269 (AerospaceMaterial Specification). Jet Reference Fluid JRF Type I, as employed fordetermination of fuel resistance, has the following composition:toluene: 28±1% by volume; cyclohexane (technical): 34±1% by volume;isooctane: 38±1% by volume; and tertiary dibutyl disulfide: 1±0.005% byvolume (see AMS 2629, issued Jul. 1, 1989, §3.1.1 etc., available fromSAE (Society of Automotive Engineers)).

In certain embodiments, compositions provide a cured product, such as asealant, exhibiting a tensile elongation of at least 100% and a tensilestrength of at least 400 psi when measured in accordance with theprocedure described in AMS 3279, §3.3.17.1, test procedure AS5127/1,§7.7.

In certain embodiments, compositions provide a cured product, such as asealant, that exhibits a lap shear strength of greater than 200 psi andin some cases at least 400 psi when measured according to the proceduredescribed in SAE AS5127/1 paragraph 7.8.

In certain embodiments, a cured sealant comprising a compositionprovided by the present disclosure meets or exceeds the requirements foraerospace sealants as set forth in AMS 3277.

Furthermore, methods are provided for sealing an aperture utilizing acomposition provided by the present disclosure. These methods comprise,for example, applying a composition provided by the present disclosureto a surface to seal an aperture, and curing the composition. In certainembodiments, a method for sealing an aperture comprises (a) applying asealant composition provided by the present disclosure to one or moresurfaces defining an aperture, (b) assembling the surfaces defining theaperture, and (c) curing the sealant, to provide a sealed aperture.

Apertures, including apertures of aerospace vehicles, sealed withcompositions provided by the present disclosure are also disclosed.

In certain embodiments, an electrically conductive sealant compositionprovided by the present disclosure exhibits the following propertiesmeasured at room temperature following exposure at 500° F. for 24 hours:a surface resistivity of less than 1 ohms/square, a tensile strengthgreater than 200 psi, an elongation greater than 100%, and a cohesivefailure of 100% measured according to MIL-C-27725.

In certain embodiments, a cured sealant comprising an addition-curablecomposition provided by the present disclosure exhibits the followingproperties when cured for 2 days at room temperature, 1 day at 140° F.,and 1 day at 200° F.: a dry hardness of 49, a tensile strength of 428psi, and an elongation of 266%; and after 7 days in JRF Type I, ahardness of 36, a tensile strength of 312 psi, and an elongation of247%.

EXAMPLES

Embodiments provided by the present disclosure are further illustratedby reference to the following examples, which describe the synthesis,properties, and uses of certain perfluoroethers and compositionscomprising such perfluoroethers. It will be apparent to those skilled inthe art that many modifications, both to materials, and methods, may bepracticed without departing from the scope of the disclosure.

Example 1 Diallyl Ether of Fluorolink®-D

Perfluoroether diol Fluorolink®-D (Solvay) was extracted five times withan equal weight of isopropanol. Removal of solvents from the polymericportion provided diol fractions of higher molecular weight. Allylationof the diol was accomplished by following a modified version of theprocedure for allylation of phenol described by Wu et al., Ind. Eng.Chem. Res., 1995, 34 (5), 1536-1538. The diallyl ether was estimated tohave a molecular weight from about 3,500 to about 4,200, based onmultiple lots.

Example 2 Synthesis of Olefin Intermediate

The diallyl ether of Example 1 (150 g, 0.0357 moles) was charged into a250-mL, 3-necked, round-bottomed flask. The flask was equipped with astirrer, a temperature probe, and a gas-adapter. The polymer wasevacuated at 66° C./7-8 mmHg for 1 hr and cooled to room temperature.The vacuum was released under nitrogen, a solution of platinum catalyst(0.1 g, PC075, United Chemical Technologies) in α,α,α-trifluorotoluene(0.5 mL) was added, and the contents were stirred at room temperaturefor 1 hr. 1,3-Bis(trimethylsiloxy)-1,3-dimethyldisiloxane (5.727 g,0.0202 mole, Gelest) was added along with 0.5 mL ofα,α,α-trifluorotoluene and the reaction mixture was stirred at roomtemperature for 9.5 hr. The viscosity of the reaction mixture was 1.84poise. Another portion (0.2 g) of1,3-bis(trimethylsiloxy)-1,3-dimethyldisiloxane (total amount: 1.927 g,0.0209 mole) was added along with 0.5 mL of α,α,α-trifluorotoluene andthe reaction mixture was heated at 38-39° C. for 3 hr. The viscosityincreased slightly to 1.94 poise. Phenyl tris(dimethylsiloxy)silane(1.571 g, 0.0048 mole, Gelest) was introduced along with 0.5 mL ofα,α,α-trifluorotoluene. The reaction mixture was heated at 38-39° C. for13.5 hr and evacuated (vacuum: 7-8 mmHg) for 1 hr to provide an olefinintermediate having a viscosity of 7.32 poise, a theoretical olefinequivalent of 9438, and a theoretical functionality of about 2.8.

Example 3 Synthesis of Moisture-Curable Polymer I

A freshly prepared sample of the olefin intermediate of Example 2 (40 g;0.0015 mole) was charged into a 100-mL, 3-necked, round-bottomed flask.The flask was equipped with a stirrer, a temperature probe, and agas-adapter. The freshly prepared sample of olefin intermediatecontained a platinum catalyst and no additional catalyst was addedduring the hydrosilylation reaction. While stirring,methyldimethoxysilane (1.4 g; 0.0132 mole) was added and the mixture wasstirred for another hour. The reaction mixture was heated at 74° C. for5 hr and cooled to room temperature. Another portion (0.4 g, 0.0038mole) of methyldimethoxysilane was added and heating was continued at74° C. for 8 hr. The reaction mixture was then cooled to 60° C. andevacuated (vacuum: 7-8 mmHg) for 1 hr to provide a moisture-curablepolymer I having a viscosity of 20.6 poise.

Example 4 Synthesis of Tetrafunctional Polymeric Silane

The diallyl ether of Example 1 (20 g, 0.0055 moles) was charged into a100-mL, 3-necked, round-bottomed flask. The flask was equipped with astirrer, a temperature probe, and a gas-adapter. The flask was flushedwith dry nitrogen. A solution of platinum catalyst (PC075) (0.015 g) inα,α,α-trifluorotoluene (1 mL) was added and the contents were stirred atroom temperature for 45 min. Phenyl tris(dimethylsiloxy)silane (4 g,0.0121 mole) was introduced and the mixture was stirred for 10 hr.Another portion of the platinum catalyst PC075 (0.15 g dissolved in 1 mLof α,α,α-trifluorotoluene) was added and stirred at room temperature for8 hr. The reaction mixture was washed with two, 20 mL portions oftoluene to remove the catalyst and unconsumed silane. Removal ofresidual solvents under vacuum (1 hr at room temperature/7-8 mmHg)provided a clear polymer having a viscosity of 4.43 poise.

Example 5 Synthesis of Olefin for Addition Curing

The diallyl ether of Example 1 (80 g, 0.0219 moles) was charged into a100-mL, 3-necked, round-bottomed flask. The flask was equipped with astirrer, a temperature probe, and a gas-adapter. The flask was flushedwith dry nitrogen. A solution of platinum catalyst (PC075) (0.015 g) inα,α,α-trifluorotoluene (1 mL) was added and the contents were stirred atroom temperature for 1 hr.1,3-Bis(trimethylsiloxy)-1,3-dimethyldisiloxane (3.515 g, 0.124 mole)was added along with 1 mL of α,α,α-trifluorotoluene. The reactionmixture was stirred at room temperature for 1.5 hr and at 43-48° C. for5 hr. At this stage, the viscosity of the reaction mixture was 2.44poise. Phenyl tris(dimethylsiloxy)silane (0.964 g, 0.0029 mole) wasintroduced with 0.5 mL of α,α,α-trifluorotoluene and the mixture stirredat room temperature for 1 hr and then at 47-48° C. for 7 hr. Removal ofthe solvents under vacuum (1 hr at room temperature/7-8 mmHg) provided aliquid polymer having a viscosity of 19 poise and a theoreticalfunctionality of 2.8.

Example 6 Tin Catalyst for Moisture-Cured Sealant

A mixture of dibutyltin dioxide (34.72 g), wetting and dispersingadditive Dysperbyk® 110 (16.67 g) and 1-butanol (6.94 g) was milledusing a high speed mixing blade until a suitable dispersion formed.Perfluoropolyether oil, Demnum™ S-200 (27.78 g, Daikin Industries), anddistilled water (13.89 g) were added in sequence and each addition wasfollowed by further milling.

Example 7 Moisture-Cured Sealant I

A polymer mix was prepared by mixing the moisture-curable polymer I ofExample 3 (37.1 g) with Demnum™ S-200 (3.71 g). Separately, a filler mixwas prepared by pulverizing a mixture of calcium carbonate (7.42 g), rediron oxide (1.484 g), zinc oxide (1.484 g), and triphenylimidazole (heatstabilizer, 0.371 g), followed by mixing with carbon black (6.678 g). Abase was prepared by bench-milling the polymer mix with small portionsof the filler mix. Base was then bench-milled with the catalyst (0.6 g)of Example 6 and a flow-out was made. The flow-out was cured at roomtemperature for 3 days and then at 140° F. for 4 days. The properties ofthe cured composition were as follows: hardness: 25 (Shore A);elongation (325%); and tensile strength: 200 psi. A small piece of thecured specimen was maintained at 177° C. for a qualitative estimate ofthe thermal properties. The specimen lost 7% of its original weightafter 3,652 hr.

Example 8 Moisture-Curable Polymer II

The diallyl ether of Example 1 (40 g, 0.0095 mole) was charged into a100-mL, 3-necked, round-bottomed flask. The flask was equipped with astirrer, a temperature probe, and a gas-adapter. The flask was flushedwith nitrogen. While stirring, a solution of platinum catalyst (0.04 g,PC075) in α,α,α-trifluorotoluene (0.5 mL) was added and the contentswere stirred at room temperature for 1 hr.1,3-Bis(trimethylsiloxy)-1,3-dimethyldisiloxane (1.553 g, 0.0055 mole,Gelest) was added along with 0.5 mL of α,α,α-trifluorotoluene. Thereaction mixture was stirred at room temperature for 1 hr and then at49-50° C. for 2.5 hr. Phenyl tris(dimethylsiloxy)silane (0.426 g, 0.0013mole) was introduced with 1 mL of α,α,α-trifluorotoluene and thereaction mixture was heated to 49-50° C. for 7 hr. Evacuation of thereaction mixture (room temperature to 50° C./40 min, vacuum: 7-8 mmHg)provided an olefin intermediate. Methyldimethoxysilane (1.5 g; 0.0132mole) was added along with 1 mL of α,α,α-trifluorotoluene at 50° C.Heating was continued at 50° C. for 4 hr and then at 79° C. for 2.5 hr.Evacuation of the reaction mixture provided moisture-curable polymer II.

Example 9 Moisture-Cured Sealant II

Moisture-curable polymer II of Example 8 (38 g) was bench-milled withtriphenylimidazole (heat stabilizer, 0.38 g) and calcium carbonate (7.6g). Carbon black (6.84 g), red iron oxide (1.52 g), zinc oxide (1.52 g)and Demnum™ S-200 (3.8 g) were added in sequence and each addition wasfollowed by bench-milling. The tin catalyst (0.6 g) of Example 6 wasthen bench-milled with the mixture and a flow-out was made. The flow-outwas cured in an atmosphere of high humidity/room temperature for 4 days.The properties of the cured composition are as follows: hardness: 33(Shore A); elongation: 287%; tensile strength: 221 psi. Cured sampleswere used to determine the changes in the physical properties uponexposure at 177° C. and immersion in JRF Type I as well as in Skydrolhydraulic fluid (Skydrol LD-4). The results are presented in Table 1 andTable 2.

TABLE 1 Exposure of Moisture-Cured Sealant II to JRF Type I and SkydrolFluid (LD-4) Exposure of Sealant to JRF Type I and Skydrol Fluid (LD-4)Tensile Strength Exposure Elongation (%) (psi) One week in JRF Type I208 84 5 days in Skydrol (LD-4) 400 Acceptable

TABLE 2 Exposure of Moisture-Cured Sealant II to 177° C. Exposure at177° C. Tensile Strength Hours at 177° C. Elongation (%) (psi) 0 287 2211,000 140 227 1500 100 236 2,382 87 244

Example 10 Addition-Curable Sealant

A mixture of three fillers, calcium carbonate (2.30 g), red iron oxide(1.33 g) and zinc oxide (1.66 g), were milled into a fine powder. In aseparate cup, the olefin intermediate of Example 5 (10.0 g), the silanepolymer of Example 4 (2.1 g), and the perfluoroether fluid Demnum™ S-200(1.21 g) were charged and mixed. Filler was mixed, in three portions,with the polymeric part. Platinum catalyst (0.025 g of 3.28% solution ofPC075 in α,α,α-trifluorotoluene) was added. The contents were mixed andspread in a plastic lid (diameter: 2.5 inches). Curing the spread for 4days at room temperature and then 24 hr at 70° C. provided anelastomeric specimen. The cured specimen lost 1.17% of its originalweight after exposure at 135° C. for 2 months.

Finally, it should be noted that there are alternative ways ofimplementing the embodiments disclosed herein. Accordingly, the presentembodiments are to be considered as illustrative and not restrictive.Furthermore, the claims are not to be limited to the details givenherein, and are entitled their full scope and equivalents thereof.

What is claimed is:
 1. An addition-curable composition comprising: (a)an alkenyl-terminated perfluoroether; and (b) a hydrosilane-terminatedextended perfluoroether, wherein the hydrosilane-terminated extendedperfluoroether comprises a compound having the structure of Formula (9);A-CH₂—CH₂-PFE-CH₂—CH₂-A′-CH₂—CH₂-PFE-CH₂—CH₂-A  (9) wherein: each A- isindependently selected from a moiety of Formula (2c):

wherein: each R¹ is independently selected from C₁₋₄ alkyl, C₅₋₆cycloalkyl, phenyl, and —O—Si(R²)_(3-m)(H)_(m), wherein each R² isindependently C₁₋₄ alkyl; and m is selected from 0, 1, and 2; and n isan integer from 1 to 6; -A′- comprises a moiety of Formula (2b):

wherein: each R¹ is independently selected from C₁₋₄ alkyl, C₅₋₆cycloalkyl, phenyl, and —O—Si(R²)_(3-m)(H)_(m), wherein each R² isindependently C₁₋₄ alkyl; and m is selected from 0, 1, and 2; and n isan integer from 1 to 6; and —CH₂—CH₂-PFE-CH₂—CH₂— is derived from analkenyl-terminated perfluoroether CH₂═CH₂-PFE-CH₂═CH₂ wherein -PFE-comprises perfluoroether groups.
 2. The addition-curable composition ofclaim 1, wherein the alkenyl-terminated perfluoroether comprisesperfluoroether groups selected from —[—CF₂—CF₂—CF₂—O—]_(k)—,—CF₂—O—[—CF₂—CF₂—O—]_(k)—[—CF₂—O—]_(k)—CF₂—, —[—CF(CF₃)—CF₂—O—]_(k)—,—[—CF₂—CF(CF₃)—O—]_(k)—, and a combination of any of the foregoing,wherein each k is independently an integer from 2 to
 100. 3. Theaddition-curable composition of claim 1, wherein the alkenyl-terminatedperfluoroether is difunctional.
 4. The addition-curable composition ofclaim 1, wherein the hydrosilane-terminated extended perfluoroether hasan average hydrosilane functionality from 3 to
 6. 5. Theaddition-curable composition of claim 1, comprising an unextendedhydrosilane-terminated perfluoroether.
 6. The addition-curablecomposition of claim 1, wherein the hydrosilane-terminated extendedperfluoroether comprises the reaction products of reactants comprising:(a) an alkenyl-terminated perfluoroether; and (b) ahydrosilane-terminated siloxane.
 7. The composition of claim 1,formulated as a sealant comprising at least one filler.
 8. An aperturesealed with the composition of claim
 7. 9. A method of sealing anaperture, comprising: (a) applying the composition of claim 7 to one ormore surfaces defining an aperture; (b) assembling the surfaces definingthe aperture; and (c) curing the composition to seal the aperture.